In connection with various large trenches, e.g. in connection with sewerage types of work or other work at the bottom of trench, it is commonly known to use so-called trench boxes. Typically, a trench box comprises two oppositely placed side walls kept at a certain distance by a number of distance struts, said trench box being arranged to prevent cave-ins on top of a person working in the trench. After digging a trench, such trench boxes are assembled and lowered, typically by means of a crane or a digger. In connection with trenches having a depth of more than 1.7 meters, it is a legal requirement in many countries to use trench boxes, whereas in less deep trenches, there are no specific requirements concerning the use of trench boxes. Common trench boxes are often large, i.e. having a height and length of more than 1.7 meters, and they are often made of steel making them heavy and completely impossible to handle without mechanical lifting equipment. Furthermore, many sewer contractors do not have access to such trench boxes. Instead, they rent the compulsory trench boxes when digging large and deep trenches. In particular, the fact that trench boxes are often an item you have to rent a couple of days prior to use means that work in trenches requiring shoring up is sometimes conducted without shoring up. The fact that people have been injured and even died in cave-ins of trenches lacking shoring up clearly proves that a solution is required which is more simple and thus easier to mount and use than the known heavy and large trench boxes.
In connection with trenches not being very deep, there is sometimes a need for and a wish to shore the walls, but since the large trench boxes are as large and heavy as they are, work is often carried out without shoring up. Alternatively, a more primitive shoring up by wooden boards and timber is used. However, such a primitive but time-consuming shoring up is often only used in trenches expected to be open for a long period. Especially when carrying out trenches in soil having been excavated previously, there is an increased risk of cave-ins of the trench. Therefore, the persons working in trenches lacking shoring up are exposed to a certain risk of injury.
Therefore, there is a great need for an appropriate and relatively light and manageable type of trench box which is especially suitable for use in trenches not being very deep, in which there is a need or wish for shoring up of the sides of the trench for various reasons.